How many digits after decimal point are needed to use SUVmax as an identifier of tumors on FDG PET-CT?

Purpose The maximum standardized uptake value (SUVmax) is often described in daily clinical reports of FDG PET-CT. We investigated whether it would be possible to localize the voxel automatically based on the SUVmax. Methods The institutional review board approved this retrospective study. We investigated a total of 112 lesions from 30 FDG PET-CT images acquired with 3 different scanners. The number of voxels showing the given SUVmax was counted, where SUVmax was provided with various degrees of precision, such as 3, 3.1, 3.14, 3.142. The effects of local maximum restriction, where only local maximum voxels were chosen, were evaluated. Results SUVmax ranged from 1.3 to 49.1 (median = 5.6, IQR = 5.2). Generally, when larger and more precise SUVmax values were given, fewer voxels were included in the range. The local maximum restriction was very effective. When SUVmax was determined to 4 decimal places (e.g., 3.1416) and the local maximum restriction was applied, 33.3% (lesions with SUVmax